Bring your eggs, milk, and butter to room temperature. I microwave the milk for 40 seconds, the butter for 15-second increments until it's softened but still firm and I place the eggs in a bowl of hot water (shells still on) for five minutes.
Preheat your oven to 375ºF and line two cookie sheets with parchment paper
Combine all spices together with the flour, salt, and baking powder and set aside.
Cream your room temperature butter and sugar together for 2-3 minutes on medium-high or until it's light and fluffy. Cold butter will not cream properly which will result in flat cookies.
While mixing on low, add in ONE room temperature egg. Let it mix in fully before adding the next to prevent your batter from curdling. Mix until smooth.
Add in your vanilla extract and mix until combined.
While mixing on low, alternate adding in the flour mixture and milk. I start with the flour and add in 1/3, then 1/2 of the milk, then 1/3 of the flour mixture, the rest of the milk, and then the rest of the flour. I like to finish the mix by hand-folding to make sure all the flour is mixed in well and the bowl is scraped. This reduces the chance of over-mixing which will cause the whoopie pies to be dry and hard.
Using a 1 Tablespoon cookie scoop, scoop your batter onto your sheet pans. I can fit about 12 per cookie sheet.
Bake your chai whoopie pies for 8-9 minutes or until the dome is just set. Don't over-bake them.
Transfer your whoopie pies to a cooling rack and let them cool down completely before you fill them.